1. Field of the Invention
The invention relates to an instrument for testing color vision in which a number of test panels of different colors arranged in pairs and transluminated by a light source having a color temperature of approximately 2400.degree.K is presented to the person to be tested.
2. Description of the Prior Art
In the known Nagel anomaloscope, two test areas are presented to the examinee, one test area appearing yellow to the person of normal color vision, emitting a spectral color of approximately 589 nm wavelength having a bandwidth of approximately .+-. 20 nm. The luminosity of this yellow area is variable by means of a displaceable neutral wedge, and is adjusted to equal the luminosity of the second test panel. The second test panel is of mixed colors constituted by a green spectral color of approximately 546 nm having a bandwidth of approximately .+-. 20 nm, and a red spectral color of approximately 671 nm having a bandwidth of approximately .+-. 20 nm. The mixing ratio is continuously variable, and the degree of an existing anomaly in color vision (red-green) can be determined from the extent of deviation from the standard values.
U.S. Pat. No. 2,453,335 describes a test device in which a test area of yellow appearance, the wavelength of the emitted rays ranging between 570 and 600 nm, is to be compared to a test area of mixed color (red-green). The wavelength of the rays emitted by the green color ranges between 520 and 550 nm, the wavelength of the red color being between 650 and 700 nm. In both prior art devices, test panels of yellow spectral color of narrow bandwidth are opposed to test panels having a mixed red-green color, the constitutents of the mixed color being red and green spectral colors of narrow bandwidths.
The examinations by means of these prior art devices are time-consuming and highly complex, and can only be effected by highly specialized personnel. The results of these extensive examination procedures can attain a high degree of precision due to the use of spectral colors of narrow bandwidths. Both devices are not suitable, however, for rapidly conducting mass examinations serving for the purpose of finding out, in a most simple method, whether the person to be examined meets specific minimum requirements regarding color perception, and of determining the nature of existing color vision defects.